Method and apparatus for amplifying or detecting electrical variations



Sept. 25, 1934. J HEANY AL 1,974,957

METHOD AND APPARATUS FOR AMPLIFYING OR DETECTING ELECTRICAL VARIATIONS Filed Dec. 11, 1951 INVENTORS 7 JOHN ALLEN Jim/van %;;T Jr. LAuRnvn .BY MM A ATTORNEY Patented Sept. 25, 1934 ares METHOD AND APPARATUS FOR AlVIPLIFY- ING, 0R DETECTING ELECTRICAL VARIA- TIONS aware Application December 11, 1931, Serial No. 580,295 9 Claims." (01. 250--27) This invention relates to electrical circuits for the communication of intelligence, particularly to circuits employing gaseous discharge devices and has special reference to the elimination of certain anti-regenerative characteristics usually present in such devices.

When it is recalled that the fundamental principle upon which regeneration is based is the phenomenon of the reaction between neighboring electrical circuits, and that in the case of a vacuum tube the inherent capacity effect between electrodes may be utilized for supplying energy from one circuit (output) to another circuit (input), it is apparent that the usual thermionic vacuum tube has an inherent tendency to regenerate. Similarly gas tubes are subject to regenerative action, the necessary coupling between output and input circuits obtains, however, by reason of the gas content being rendered conductive by ionization and is not dependent upon capacitive coupling as in the case of thermionic vacuum tubes; in fact, according to our observations we note that the relativelysmall capacitance present in gas tubes of the type described is operable to lessen or counteract the feedback provided by the conductive coupling.

In agreement with empiric data we have concluded that in the usual gas tubes there are two types of feedback, the'first and predominating type we shall designate conductive feedback as the transfer of energy from output to input apparently takes place by reason of the gas within the container having been rendered conductive by ionization. The second type we may designate as electro-static feedbachas the transfer of energy takes place by reason of the inter-electrode capacity effect. The electro-static feedback is out of phase with the conductive feedback and tends to lessen or detract from the eifectiveness of regeneration resulting from the predominating or conductive coupling between circuits.

Since it is fundamental that regenerative amplification is a function of the effectiveness of coupling between output and input circuits, it follows that by Varying the coupling the degree of amplification may be Varied. Similarly by counteracting, neutralizing, or otherwise obviating conditions inherently tending to decrease effec-y tiveness of coupling, amplification maybe increased.

A principal object of our present invention is the provision of means, exterior to gaseous discharge devices, for obviating electro-static feedback and/ or other conditions tending to decrease effectiveness of internal. conductive coupling whereby amplification may be increased within the same tube. g

It is to be noted that so called neutralizing arrangements as employed in the thermionic art to reduce capacity effect are, in the last analysis, all directed toward suppressing regeneration rather than anti-regeneration. Stated in another way, capacity effect contributes to the undesired condition of regeneration in vacuum tubes but detracts from the desired condition of regeneration in gas tubes.

In carrying our invention into effect we fmd it practical to adopt, with modifications, certain arrangements known in the vacuum tube art for suppressing regeneration, for our purpose of increasing regeneration. V I

We are not prepared to state at this time a theory which will, to our satisfaction, fully explain the results we have obtained or the phenomenon which we have observed. We suggest that in carrying our invention into practice that the inherently different characteristics of vacuum and gas tubes, as above set forth, be borne in mind.

Our invention will perhaps be more readily un'-, derstood by reference to the accompanying drawing, in which certain preferred forms of the invention are shown by way of illustration but without limiting the invention thereto.

Fig. I is a simple regenerative circuit.

Fig. II is a regenerative circuit including means for suppressing anti-regenerative characteristics usually present in gas tubes.

7 Fig. III is a modification of II.

Fig; IV is a regenerative circuit and includes means for impressing an E. M. F. upon the input circuit opposite in phase to that of the electro-.- static feedback.

Fig. V shows an inducted feedback system for overcoming rather than neutralizing electrostatic ieedback.

Fig. V1 is a regenerative circuit arrangement including a resistor common to input and output circuits for increasing regeneration.

The circuit of Fig. I is similar in many respects to that shown in our co-pending applica-' tion, Serial No. 559,214 filed August 25, 1931, disclosing a simple regenerative circuit arrangement, including a cold cathode gas tube and shows symbolically the abbreviated anode disclosed in our co-pending application, Serial No. 580,294 filed December 11, 1931. I

As disclosed in the latter application, capacity effect as well as certain other negative feedback characteristics usually present in gas tubes may be suppressed or otherwise obviated within the tube. In circuits including tubes of our improved electrode assembly it is unnecessary to resort to the use of suppressor circuits of our present invention. The circuit comprises a coupling transformer having a primary winding, 20, and a secondary winding. The terminals of secondary winding 21, which are shunted by a tuning condenser 22, are connected respectively to the grid, 5, and cathanode 8 of a gaseous cell, 1.

A balancing battery, 23, may be included in the input circuit. The cell or tube, 1, comprises an anode, 4, and a cathode element, 9, in addition to the input electrodes, 5 and 8.

A single energizing source is designated here simply by positive pole and negative poie In the circuit here shown cathanode 8 is common to both input and output circuits, the output circuit being shown symbolically between terminals 24 and 25. The conductive path for feeding back energy from output to input is through the gas within the tube, the gas having been rendered conductive by the ionizing electrodes 8 and 9. All other factors being equal, we have found that the effectiveness of regeneration in the circuit of Fig. I is greater in tubes of our abbreviated anode construction than it is in tubes having electrodes constructed and arranged in accordance with the usual cold cathode ga's'tube specifications.

In Fig. II the path of electro-static feedback which tends to lessen the eflicacy of the predominating or conductive coupling is shown symboiically by the dotted lines between electrodes 4 and'5 in the tube 1. The suppressor circuit comprises an inductance 26 and a variable capacity 27, forming tuned circuit 26--2'7. The inductance 26 and capacity 2'? are of such values as to present a path of infinite impedance to the currents tending to cause electr'o-static" feedback which might otherwise take place due to the capacity effect, but impeding in no way the predominating or conductive feedback. Capacity 28 prevents direct current in the output circuit from flowing in tuned circuit 2627.

Fig. III is similar in all respects to Fig. II with the exception that instead of having a separate suppressor control (variable condenser 27 of Fig. II) the tuned circuit is combined with the input 3 circuit thereby simplifying both construction and operation of the circuit.

In the embodiment of our invention shown diagrammatically in Fig. IV, the circuit isdesigned to neutralize rather than suppress negative feedback, that is, we provide a coupling exterior to the tube between output and input electrodes whereby an electro-motive force opposite in phase to that traversing the internal capacity path is operable to neutralize the undesired electrostatic energy. The operation of this circuit appears to agree with the general formula: A-b+C=A(Cb), wherein A=conductive feedback energy; b=electr0-static feedback en ergy; C=neutralizing feedback energy.

In Fig. V an external inductive feedback supplements the coupling provided by the ionized gas within the tube whereby the effect of the undesired electro-static coupling is overcome rather than suppressed or neutralized. The external coupling obtains by reason of the tickler coil 29 arrangement shown in electrical association with input inductance 21.

Fig. VI discloses still another method of increasing the degree of coupling between output '3 and input circuits and shows a variable resistance,

30, common to both input and output circuits.

.The value of this resistance 30 may vary somewhat in different tubes and may be adjusted accordhng to the degree of feedback desired. We have found that in gas tubes for the radio frequency stage of the usual broadcast receiving sets that the proper value of resistance to be of the order of 5,000 ohms, more or less. If the value of resistance 30 is considerably above 5,000 ohms, we find that the degree of regeneration decreases with increased resistance.

As many further modifications andchanges in detail will suggest themselves to those skilled in the arts to which our invention pertains, without departing from the spirit and scope of our invention, it is'to be understood that the foregoing is to be interpreted as illustrative and not in a limiting sense, except as required by the appended claims and by the prior art.

What is claimed is: V

I. The method of operating a gaseous discharge device having a cathode, cathanode, grid, and anode, between which electrodes exists an inherent electrostatic coupling producing an antiregenerative feedback, which comprises feeding back to the input *electrode energy which is in phase with the signalling energy applied to said input electrode but isout of phase with the signal energyfed back to the input electrode through the said inherent capacity.

2. In an electrical amplifying system having input and outputcircuits,terminals therefor immersed in a' gas, a cathode, a cathanode, a grid, and an anode connected to said terminals, said gas providing a conductive coupling between said electrodes, and said electrodes havin an inherent electrostatic coupling therebetween independent of said conductive coupling, said electrostatic coupling normally diminishing the GfiiCELCY of said conductive coupling to produce reaction of the output circuit on the input circuit, and means connected tosaid output circuit and in electrical association with said input circuit for suppressing the anti-regenerative effect of said inherent electrdstatic coupling whereby the overall amplification of said system is increased. 7

3. In combination, a gaseous conduction device having acathode, grid, cathanode, and anode, means for causing said device to regenerate and including an ionizable conductive medium between said electrodes, and circuit connections between said electrodes in parallel with the inherent capacity therebetween to provide with said inherent capacity a path between said electrodes which is resonant to the frequency of the energy to be fed back.

4. The combination according to claim 3 in which the circuit means is external to the conductive medium. r H

5. In combination, a gaseous conduction device having an anode, cathode, grid, and cathanode, means for ionizing the space between said electrodes, said electrodes having appreciable electrostatic coupling areas acting anti-'regeneratively with relation to the normal regenerative gas conduction therebetween, and means including a tuned circuit in series with a condenser connected between said electrodes to provide with said electrostatic coupling a path between electrodes.

6. In combination, a gaseous'conductor device having a cathode, grid, cathanode, and anode, said electrodes having appreciable inherent electro-static coupling surfaces acting anti-re :ass

said

generatively with relation to the normal regenerative conductive coupling between said electrodes, a circuit connecting said output electrode with said control electrode and having a predominating inductance characteristic to provide with said electrostatic coupling a path between said electrode which is resonant to the anti-regenerative feedback tending to flow through said coupling.

7. In combination, a gaseous conduction device having an anode, a cathode, a control electrode, and a cathanode, an ionizable medium in which all of said electrodes are immersed, an inductance and a capacity connected in series between said anode and said control electrode and a connection from a point intermediate the ends of said inductance to said cathode for feeding back to said control electrode energy which is out of phase with the energy tending to be fed back through the inherent electrostatic coupling between said anode and control electrode.

8. The combination according to claim '7 in which the capacity in said series connection is variable to control the degree of feedback from the output electrode to the control electrode.

9. In combination a vessel containing a filling of a conducting gas, an anode and a cathode mounted in spaced relation within said device, another pair of electrodes within said vessel, one of said electrodes act ng as a control electrode for said anode, a tuned input circuit connected across said other pair of electrodes, said control electrode and said anode having an inherent electrostatic capacity therebetween tending to produce an antiregenerative effect back from the anode to said input circuit, and means connected to said anode externally of said vessel for feeding back to said input circuit energy which is opposite in phase to the energy tending to feedback through said inherent coupling.

JOHN ALLEN HEANY. HERBERT ST. LAURENT. 

